Palaeomagnetic polarity sequences have been determined for the lower Yuendumu Sandstone of the Ngalia Basin, and the upper Wonnadinna Dolomite and lower Gnallan-a-gea Arkose of the Georgina Basin to illustrate an application of magnetostratigraphy, i.e. to test previous correlations. The Yuendumu Sandstone of the Ngalia Basin had been correlated with the Arumbera Sandstone because of lithological similarities, as well as palaeogeographic and tectonic considerations. The discovery of trace fossils in the upper Yuendumu Sandstone had supported a correlation with the upper, Cambrian, part of the Arumbera Sandstone. The age of the lower Yuendumu Sandstone was unknown. It was found to be of mixed polarity with a marked normal bias. Magnetostratigraphic comparisons with the polarity pattern from the Amadeus Basin are equivocal: they allow correlations with both the upper part of Arumbera Sandstone I (latest Proterozoic), and the Arumbera Sandstone II-III (Early Cambrian). Since Arumbera II lies unconformably on Arumbera I, we searched for a break within the Yuendumu Sandstone. Photointerpretation and field observation revealed an unconformity within the formation, which, together with the palaeomagnetic data, indicates that the lower part of the sandstone is best correlated with the upper part of Arumbera Sandstone I, and thus is of latest Proterozoic age. The polarity pattern from the Georgina Basin stimulated a reassessment of possible correlations and the collection of new field data. The magnetostratigraphic test was to check whether the reversely magnetised Julie Formation of the Amadeus Basin correlated with the Wonnadinna Dolomite of the Georgina Basin. The magnetostratigraphic result was negative; the Wonnadinna Dolomite is predominantly normally magnetised. This led to an examination of drill cores from near Mount Skinner on the Alcoota 1:250 000 Sheet area, which showed that the Grant Bluff Formation, which elsewhere overlies the Gnallan-a-gea Arkose and the Wonnadinna Dolomite, occurs at depth below correlatives of Arumbera I, the Julie Formation and the upper Pertatataka Formation. It now appears that the Grant Bluff Formation and the Gnallan-a-gea Arkose (Georgina Basin) are correlatives of the Cyclops and Waldo Pedlar Members of the Pertatataka Formation (Amadeus Basin). The Wonnadinna Dolomite is thought to be a correlative of the cap dolomites above the upper tillites of the Ngalia and Amadeus Basins. The new Adelaidean stratigraphy of the central Australian basins has immediate application with regard to Adelaidean Polarity Time Scales; it allows for partial coverage back to the time of the upper glaciation of the late Proterozoic.
